Please help solve the mystery of 5.5% vs 3.2% Beer!?

Question

Since I was in high school I remember many discussions and arguments about 5.5 and 3.2 beer. I am originally from Kansas (USA) and with it being a dry state they provide 3.2% beer in Gas Stations and Grocery Stores and at liquor stores they provide 5.5% beer. As youngins high schoolers would make jokes that you got drunk off that lame 3.2% beer. However, I remember a more scientific discussion with a friend that difference is a measurement by VOLUME and WEIGHT. The 5.5% measurement is by volume and the 3.2% measurement is by weight. So, if that is the case, what is the difference in alcohol content between the two beers. Is one a supreme lightweight if he were to get drunk off of 3.2% beer or is he actually getting drunk because the alcohol available in both beers is similar? I would prefer people with a scientific / chemistry back ground to answer but if you know the answer or have any helpful input, by all means answer.

Thanks everyone!

Answer 1

Very Good Question! I bet you were drunk when you and your friends started discussing this matter. lol.

EXPLANATION:
See, the density of average beer is about 1.050 g/cm3. So, given 355ml of beer (a can size beer) and density of EtOH, which is 0.789g/ml, we can figure out the total mass of EtOH (ethanol) contained within the each beer.

CALCULATION:
The 5.5% beer has:
355ml beer (5.5ml EtOH/100ml beer)(0.789g EtOH/1ml EtOH) = 15.405g EtOH.

Now lets figure out how many grams of alcohol is contained within the beer that has 3.2% alcohol by mass:
355ml beer (1.050g beer/1ml beer)(3.2gEtOH/100gbeer) = 11.928g EtOH.

CONCLUSION:
A 355ml (12oz) can of beer that contains 5.5% alcohol by volume has 15.405g of the happy juice.
A 355ml (12oz) can of beer that contains 3.2% alcohol by mass has only 11.928g of happy juice.

From the finding, it can be concluded that broke college students need to buy their beer from the liquor store. The beer from the liquor store (5.5% by volume) is 22.6% more bang for the buck compared to the beer from the grocery Stores (3.2% by mass).

Now, I can rest assured that my 40K college education was put in good use... damn I need a beer. Cheers!

Answer 2

yes alcohol content is only ever measured as a % volume/alcohol by volume (ABV) or by proof.

Ethanol is the chemical name for what is commonly referec to as alcohol. As ethanol is a liquid and not a solid the % volume is a % volume/volume calulation.
10ml of ethanol in 100 ml total volume would give you a 10% volume alcoholic liquid.

In the UK we calculate how much alcohol is in something using the Units scale. 1 unit is equal to 10ml of ethanol, so a 1 litre bottle of 37.5% vodka would be 37.5 units. The maximum recommendation over here is 3 units a day for males and 2 for females.

If as you say the 3.2% beer was measured by weight then I have absolutely no idea why it just over complicates things.

Answer 3

If you look at the can/bottle of a 3.2% beer you'll see that it's measured by volume so a 3.2% has lesser alcohol content than 5.5% that's why 3,2% is available in gas stations because it's not a strong beer.